Method of producing free-flowing compositions containing an alkali metal monopersulfate and the composition produced thereby



United stat P f p MONOPERSULFATE AND THE COMPOSITION PRODUCED THEREBY 3 2,932,555 Esta e A.

- containing 0.5% by weight or more of magnesium oxide Stephen E. .Stephanoti, Lewiston, N.Y., assignor to E. I.

du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application Februarys, 1956 Serial No. 563,191

Claims. cilia-114 No Drawing.

This invention relates to" non-cakingsolid compositions containing the monopersulfates of alkali metaL.

remain free-flowing when stored under ambient room conditions in vented bottles for six months. Control samples containing no adjuvant cake badly within a few days under the same condition.

The adjuvant may be supplied to'the dry monopersulfate composition in anyisuitablemanner. Mixing dry powders of the monopersulfate and the adjuvant followed. by tumbling the product in a rotating mixer is quite satisfactory. Mixing the adjuvant with a slurryor solution containing dissolved monopersulfates is less satis- Solid oxidizing agents based on'monopersulfates have recently become available. "The monopersulfates arethe salts of monopersulfuric or Caros acid, H 80 m WhlCh one of the hydrogen atoms has been replaced. The most common representatives of the group are NaHSO and elfective oxidizing agents, they are somewhat hygroscopic.

As they pick up moisture from the air they tend to cake, yielding agglomerates whichdestroy the free-flowing char acteristics of the material. Sincethe powder is valuable in bleaching'and laundering compositions, the necessity for the freedom to run or flow is obvious. v i Y 1 A primary object of theprescm 6 5. 7,

quently, provision of a methodof imparting the chafaci' teristic or free-flow to compositions containing monopersulfates, the monopersulfatesof the alkali metals in particular. V j

Another object is provision of monopersulfate compositions which are free-flowing in nature.

The above-mentioned and yet other objects are achieved 0 Y K carryinginitially 5% active? oxygen. Generally these alkaline compositions will contain enough sodium factory because of the possibility of a reaction'between the materials.

'The anti-caking agent of this invention is eiiective not.

only with pure monopersulfates but also with monoper sulfates containing inert diluents, i. e. diluents possessing noactive oxygen. The corresponding sulfates and bisulfates have already been noted as generally present in the monopersulfate. The mole ratio KHSO :KHSO :K SO is generally chosen as about 2:1:1 but other ratios can be "employed as shown by copending application S.N. 549,629, filed November '29, 1955. The acid compositions are formed to possess roughly'between aboutland 10% by weight of active oxygen and about 10-90% by weightof the bis-ulfate. V

In addition to the sulfates and bisulfates, alkaline compounds such as the water-soluble members of, the group consisting of alkali metal phosphates, silicates, and carbonatesa're frequently added to counteracttheacidily of the monopersulfates in aqueous solution. Sodium or potassium tripolyphosphates, orthophosphates, metaphosphates, pyrophosphates, and other alkaline phosphates, metaand orthosilicates, and carbonates, bicarbonates and sesquicarbonates are representative of these alkaline diluents but others may also be used. I Borax for example may be included in the mixture.

A typical formulation containing about 2% active oxy-:

gen by weight may be made up from 42% sodium carbonate, 11%' sodium tripolyphosphate, 1% magnesium inaccordance with'this invention by the incorporationin the monopersulfate-containing mixtures of certain alka ine compounds of magnesium and sodium. These compounds may be divided into two groups. The first group co n-1 prises alkaline inorganic magnesium compounds," e.g'., magnesium I oxide and theclosely' related magnesium hydroxide andmagnesiuincarbonate. Theisecond group comprises alkaline magnesium and sodium salts of monoand dibasic organic acids, fatty acids in particular. The acids should possess betweenzS and. 20 carbon .1 atoms. Representative of this second group are magnesium stearate and oleate and sodium'adipate,' stearate and sebacate. Magnesium oxide and the closely related compounds are greatly preferred since-they alone of those mentioned are odorless. They are, furthermore, more etfective as anti-caking aids.

The quantity of adjuvants needed is not sharply critical and may be referred to as an efiective anti-caking amoun Generally this amount is between about'0.5 and 10% by weight of the weight of the monopersulfate composition to which it is added. Between about 0.5

and 2.0% by weight is usually satisfactory and preferred oxide and 46% of a mixture of KHSO KHSQ; and

or potassium monopersulfate to give an over-all active oxygen percentage of 17.5%, i.e. about Iii-% by weight, andaremainderof the diluents mentioned. The

alkaline diluents are discussed at length in copending application 563,177, filed of common date herewith. In the absence of an anti-caking agent, monopersulfate compositions containing these alkaline diluents may cake ifTthe active oxygen content is as low as about 2or 3%.

The adjuvants of this invention are primarily of value in compositions containingthefmonopersulfate of an alkali metal. They may, however, be used with other monopersulfates as well. Of the f k li metal, salts, those of sodium,--'p'otassium and ammonium are themost impor'-" tant. In this specification the term alkali metals in-' cludes ammonium.

There follow someexamples which illustrate the invention in more detail. Percentages given in the examples are weight percentages.

EXAMPLE 1 Separate test samples were made up from sulfate mixtures containing about 5% of active oxygen and possessing initially the KHSO :K SO :KHSO mole ratio of from onion skin paper and sealed at one end toa heightv of 1 inch. The samples were packed by tapping the cylinders, held within a glass vial, times. The packed cylinders were placed in a desiccator held at a relative humidity of 90% and kept there for 24 hours at 40 C. The cylinders were removed from the desiccator, dried in an oven at 40 C. for 4 hours and then allowed to stand at room temperature for 1 hour at ambient humidity (ca. 20-30% The samples were rated visually as follows:

Rating 1: The sample poured out of tube easily and showed no bridging or clumping. of particles.

Rating 2: The sample poured out of tube but showed bridging and clumping.

Rating 3: The sample caked but the cake could be broken by squeezing the cylinder gently.

Rating 4: The sample produced a firm cake which required more than 100 g. pressure to crush.

Rating 5: The sample formed a solid cake which required over 1000 g. pressure to crush.

Results obtained from samples holding of the adjuvants are shown in Table I.

9 Table I.Sampies containing 10%. of adjuvant Magnesium stearate Sugar Magnesium ox Tricalcium phosphate Magnesium-aluminum silicate (china clay) Calcium silicat Sodium tripolyphosphate 3 Magnesium Sulfate 3 Control (no additive) V........ 5

EXAMPLE 2 The procedure of Example 1 was essentially repeated except that only 3% of the anti-caking agent was employed in the samples. Results are shown in Table H.

Table Il.Sampl,es containing 3% of, adjnvant Anti-caking agent: Rating Magnesium oxide 1 Magnesium stear 1 Sodium nleate I 3 Sodium adipate+10% SLS 1 Sodium sebacate+10% SLS 1 Stearic acid 3 Star h '3 Control (no additive) 5 SLS is sodium lauryl sulfate, a wettirigagentdptionally.

employed.

EXAMPLE 3 The procedure of the Examples 1 and 2 was essentially repeated except that 1% of the anticaking agent was employed. Results are shown in Table III.

Table lll.-Samples containing 1% of adjuvant Anti-caking agent: Rating Magnesium silicate 2V2 Potassium pyrophosphate 5 Magnesium oxide 1 Tricalcium phosphates 5 Silica gel (colloidal) 5 Magnesium stearate 1 Potassium sulfate 5 Potassium silicate 5 Sodium adipate+10% SLS 1 Sodium sebacate+10% SLS 1 /2 Sodium toluene sulfonate 5 Control (no additive) 4 Having described my invention, I claim:

1. The method of imparting free-flowing characteristics to a solid composition containing an alkali metal monopersulfate in an amount equivalent to at least 1% active oxygen, based upon the weight of said composition, com prising incorporatingin said composition, in an amount efiective to inhibit caking of said composition but not exceeding 10% of the weight of said composition, an anticaking agent from the group consisting of the oxide, the hydroxide and the carbonate of magnesium and the magnesium and sodium salts of stearic acid, oleic acid, adipic acid and sebacic acid.

2. The method of claim 1 employing 0.5 to 2% of the anti-caking agent.

3. The method of claim 1 wherein the monopersulfate is potassum monopersulfate.

4. The method of claim 1 wherein the anti-caking agent is magnesium oxide.

5. The method, of claimwherein the monopersulfate is potassium monopersulfate and 0.5 to 2% magnesium oxide is employed as the anti-caking agent.

6. A free-flowing solid composition containing, based upon the weight of said composition, an alkali metal monopersulfatein an amount equivalent to at least 1% active oxygen and an amount cfiective to inhibit caking of said composition but not exceeding 10% of an anticaking agent admixed therewith, said anti-caking agent being from the group consisting of the oxide, the hydroxide and the carbonate of magnesium and the magnesium and sodium salts of stearic acid, oleic acid, adipic acid and sebacic acid.

7. A composition according to claim 6 which contains 0.5 to 2% of the anti-caking agent.

8. A composition according to claim 6 in which the monopersulfate is potassium monopersulfate.

9. A composition according to claim 6 in which the anti-caking agent is magnesium oxide. I

10. A composition according to claim 6 in which the monopersulfate is potassium monopersulfate and which 2,141,189 Lind Dec. 27, 1938 OTHER REFERENCES 7 Grant: Hackhs Chemical Dictionary, 3rd ed., The Blakiston C0mpany, Philadelphia, Pa., 1944, page 292.

Lande June 7, 1927 

1. THE METHOD OF IMPARTING FREE-FLOWING CHARACTERISTICS TO A SOLID COMPOSITION CONTAINING AN ALKALI METAL MONOPERSULFATE IN AN AMOUNT EQUIVALENT TO AT LEAST 1% ACTIVE OXYGEN, BASED UPON THE WEIGHT OF SAID COMPOSITION, COMPRISING INCORPORATING IN SAID COMPOSITION, IN AN AMOUNT EFFECTIVE TO INHIBIT CAKING OF SAID COMPOSITION BUT NOT EXCEEDING 10% OF THE WEIGHT OF SAID COMPOSITION, AN ANTICAKING AGENT FROM THE GROUP CONSISTING OF THE OXIDE, THE HYDROXIDE AND THE CARBONATE OF MAGNESIUM AND THE MAGNESIUM AND SODIUM SALTS OF STEARIC ACID, OLEIC ACID, ADIPIC ACID AND SEBACIC ACID. 